"All 71 ATR pilots will take part in proficiency tests carried out by the CAA and third-party professionals for an estimated four days," TransAsia Airways said in a statement (in Chinese).

The aviation regulator has also ordered engine and fuel system checks on the remaining 22 ATR-manufactured planes currently in active service on the island.

More bodies found

Five more bodies were retrieved from the Keelung River yesterday, bringing the total toll to 40, the Taipei fire department said.

Rescuers lift the wreckage of the TransAsia ATR 72-600 out of the Keelung river at New Taipei City on February 4, 2015. Photo: AFP

The bodies were found downriver from the crash site.

Divers and rescuers are scouring the river for three more people who remain missing. Fifteen others were rescued alive from the plane on Wednesday.

Thomas Wang, executive director of Taiwan's Aviation Safety Council, said on Friday that the plane's right engine triggered an alarm just 37 seconds after taking off from the Taipei's Songshan airport.

The main pilot could be heard on cockpit voice recordings saying the engine had experienced a "flame-out", Mr Wang said, which can occur when the fuel supply to the engine is interrupted.

However, he said data showed that the engine had in fact been moved into idle mode.

Seconds later, the pilots shut down the left engine, meaning neither engine was producing any power. A restart was attempted, but the plane crashed 72 seconds later.

Officials said it was unclear why the left engine had been turned off, especially as the plane, an ATR 72-600, is able to fly with just one functioning engine.

Mr Wang said it was too early to draw firm conclusions about why the first engine had lost power but he told the BBC that the pilots had not followed normal procedure.

Officials have praised the chief pilot, Liao Chien-tsung, who is believed to have deliberately steered the plane away from blocks of flats and commercial buildings before the crash.